Linker-controlled polymeric photocatalyst for highly efficient hydrogen evolution from water

Wang, Yiou; Bayazit, Mustafa K.; Moniz, Savio J. A.; Ruan, Qiushi; Lau, Chi Ching; Martsinovich, Natalia; Tang, Junwang

doi:10.1039/c7ee01109a

Cited by 243 publications

(174 citation statements)

References 68 publications

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“…6,8,16,17 For polymer based photocatalysts, up to now, there are many reports about proton reduction by either g-C 3 N 4 or g-C 3 N 4 doped by oxygen, boron, phosphorus, etc. 6,9,[18][19][20][21] For example, Wang et al reported that graphitic carbon nitride presents great potential for photocatalytic proton reduction in 2009 and platinum decorated g-C 3 N 4 shows ca. 10 mmol h À1 hydrogen evolution rate under visible light irradiation.…”

Section: Introductionmentioning

confidence: 99%

“…18 Later, the light absorbance of this polymer was extended to 800 nm by controlling the linker of carbon nitride and it generated H 2 by light irradiation from the ultraviolet to near infrared regions. 9 This progress in polymer photocatalysts for proton reduction has played a crucial role to stimulate research interest in polymer photocatalysts. However, the most challenging step, water oxidation, in water splitting has met with little success in polymer photocatalysis.…”

Section: Introductionmentioning

confidence: 99%

“…[26][27][28][29] However, g-C 3 N 4 shows a rather low activity for water oxidation due to its high valence band position. 6,9,18 Controlling the ratio of N to C in such a polymer photocatalyst would induce both a band gap change and band position shift. Only a few reports have considered the N to C ratio by introducing nitrogen vacancies.…”

Section: Introductionmentioning

confidence: 99%

“…[30][31][32] However, most of those cannot lower the valence band of g-C 3 N 4 , because the N replacements are mostly on the linker, -NH x groups, mainly contributing to the n-p* transitions, which are far less active than the p-p* transitions of N in the heptazine units. 9,33,34 A covalent triazine-based framework (CTF-1) is composed of alternating triazine units and phenyl groups in a 12-membered conjugated ring system, as shown in Fig. 1a.…”

Section: Introductionmentioning

confidence: 99%

“…7,8 Compared with the above single photocatalyst a Department of Chemical Engineering, University College London, Torrington Place, for pure water splitting, a Z-scheme composed of two photocatalysts responsible for two half reactions promises 10% higher solar-to-fuel conversion efficiency. [9][10][11][12][13] Therefore, substantial efforts have recently been channeled into searching for efficient polymer photocatalysts for either proton reduction or water oxidation in an attempt to construct an efficient Z-scheme system. Therein, water oxidation has been widely accepted as the rate-determining step in water splitting, and thus it is more challenging and important than proton production.…”

Section: Introductionmentioning

confidence: 99%

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Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Xie

Shevlin

Ruan

et al. 2018

Energy Environ. Sci.

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251

188

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aWater oxidation is a rate-determining step in solar driven H 2 fuel synthesis and is technically challenging to promote. Despite decades of effort, only a few inorganic catalysts are effective and even fewer are effective under visible light. Recently, attention has been paid to synthetic semiconducting polymers, mainly on graphitic C 3 N 4 , with encouraging hydrogen evolution performance but lower activity for water oxidation. Here, a highly ordered covalent triazine-based framework, CTF-1 (C 8 N 2 H 4 ), is synthesised by a very mild microwave-assisted polymerisation approach. It demonstrates extremely high activity for oxygen evolution under visible light irradiation, leading to an apparent quantum efficiency (AQE) of nearly 4% at 420 nm. Furthermore, the polymer can also efficiently evolve H 2 from water. A high AQE of 6% at 420 nm for H 2 production has also been achieved. The polymer holds great potential for overall water splitting. This exceptional performance is attributed to its well-defined and ordered structure, low carbonisation, and superior band positions. Broader contextSplitting water by sunlight is an attractive renewable approach to generate clean hydrogen for producing chemicals or powering vehicles. This ultra-pure hydrogen also avoids the dreaded catalyst poisoning, which occurs even with very low levels of CO residuals from fossil-fuel generated hydrogen. The key challenge to sustain continued hydrogen generation from this artificial photosynthesis process is to speed up the water oxidation reaction, which is hard to proceed due to multiple electron transfer steps. Oxidation catalysts based on polymeric semiconductors are particularly promising for this purpose because of their abundance leading to low cost, tunable band structure to match the solar spectrum and variable degree of conjugation to impact on the p-p* excitation for efficient electron transfer. With a moderate microwave assisted strategy, we are able to control the degree of conjugation and minimise the undesirable structural carbonisation of a new type of polymeric photocatalyst-covalent triazine-based framework. The optimised catalyst shows advantageous band positions, to capture a wide spectrum of visible light and enhance the charge separation efficiency, leading to very high water oxidation and hydrogen evolution capabilities. The overall discovery paves the way for the development of efficient and continuous clean hydrogen production from the renewable visible-light water splitting process.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Xie

Shevlin

Ruan

et al. 2018

Energy Environ. Sci.

Self Cite

251

188

View full text Add to dashboard Cite

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Effective Prevention of Charge Trapping in Graphitic Carbon Nitride with Nanosized Red Phosphorus Modification for Superior Photo(electro)catalysis

Jing

Zhu

Phillips

et al. 2017

Adv Funct Materials

215

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The high occurrence of trapped unreactive charges due to chemical defects seriously affects the performance of g-C 3 N 4 in photocatalytic applications. This problem can be overcome by introducing ultrasmall red phosphorus (red P) crystals on g-C 3 N 4 sheets. The elemental red P atoms reduce the number of defects in the g-C 3 N 4 structure by forming new chemical bonds for much more effective charge separation. The product shows significantly enhanced photocatalytic activity toward hydrogen production. To the best of our knowledge, the hydrogen evolution rate obtained on this hybrid should be the highest among all P-containing g-C 3 N 4 photocatalysts reported so far. The trapping and detrapping processes in this red P/g-C 3 N 4 system are thoroughly revealed by using time-resolved transient absorption spectroscopy. P modification was thoroughly investigated by using timeresolved transient absorption (TA) experiments.The authors declare no conflict of interest.

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An Unusual Red Carbon Nitride to Boost the Photoelectrochemical Performance of Wide Bandgap Photoanodes

Yang

Wang

Jiao

et al. 2018

Adv Funct Materials

113

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Tuning the bandgap of a semiconductor to achieve strong band-to-band visible light absorption is highly desirable but challenging for photocatalysis. This work presents a facile molten-salt-assisted route to prepare red-colored polymerized carbon nitride (RPCN) nanosheets with a remarkable redshifted absorption and narrowed bandgap of 1.9 eV. Both experimental findings and theoretical calculations reveal that alkali heteroatoms are effective to tune the surface and electronic structures of carbon nitride, resulting in significantly reduced bandgap and excellent solubility. The RPCN-sensitized TiO 2 nanorod-based photoanode generates an impressive photocurrent density of ≈2.33 mA cm −1 at 1.23 V versus reversible hydrogen electrode under Air Mass 1.5 G illumination without any cocatalyst, which is 2.6 folds higher than that of the bare TiO 2 photoanode. The new findings in this work could inspire the electronic structure engineering of semiconductor photocatalysts to greatly enhance the visible light absorption and provide a generic strategy to enhance the photoelectrochemical performance of wide-bandgap semiconductor photoelectrodes.

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Linker-controlled polymeric photocatalyst for highly efficient hydrogen evolution from water

Abstract: A linker-controlled strategy has been demonstrated to synthesize polymeric photocatalysts for efficient H2 evolution by UV-Vis-IR with benchmark quantum yields.

Cited by 243 publications

References 68 publications

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Effective Prevention of Charge Trapping in Graphitic Carbon Nitride with Nanosized Red Phosphorus Modification for Superior Photo(electro)catalysis

An Unusual Red Carbon Nitride to Boost the Photoelectrochemical Performance of Wide Bandgap Photoanodes

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